Optically active 1-alkyl-substituted 2,2,2-trifluoroethylamine, which is the target of the present invention, is an important intermediate of medicines and agricultural chemicals.
As processes for producing optically active 1-alkyl-substituted 2,2,2-trifluoroethylamine, there are reports of (1) a process (Patent Publication 1 and Non-patent Publication 1) in which (S)—N-(1-alkyl-2,2,2-trifluoroethylidene)-1-phenylethylamine is subjected to a [1,3]-proton shift reaction in the presence of a base, followed by hydrolysis; (2) a process (Patent Publication 2) in which a racemic mixture of 1-methyl-2,2,2-trifluoroethylamine is subjected to optical resolution with D-tartaric acid; (3) a process (Patent Publication 3) in which a carboxylic acid of L-alanine is fluorinated by SF4; and (4) a process (Non-patent Publication 2) in which (R)-sulfinylimine is subjected to an asymmetric trifluoromethylation by trimethyl(trifluoromethyl)silane (TMSCF3), followed by hydrolysis.
Patent Publication 1: Japanese Patent 3005669
Patent Publication 2: United States Patent specification 6204269
Patent Publication 3: European Patent Laid-open specification 0323637
Non-patent Publication 1: J. Org. Chem., (US), 1997, Vol. 62, No. 10, p. 3030-3031
Non-patent Publication 2: Angewandte Chemie, International Edition, (Germany), 2001, Vol. 40, No. 3, p 589-590
In the processes of Patent Publication 1 and Patent Publication 2, it was necessary to use 1 mol or more of expensive DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) relative to 1 mol of the reaction substrate in order to obtain high chirality induction, and a purification by silica gel column chromatography was necessary to remove it.
In the process of Patent Publication 2, non-natural type tartaric acid as a resolving agent was expensive, and it was difficult to recover and reuse the same due to its water solubility. The theoretical yield was not greater than 50% due to optical resolution, and a complicated operation was necessary for racemization of an unnecessary isomer. In the process of Patent Publication 3, it was necessary to use dangerous SF4, and the yield was not so high. In the process of Non-patent Publication 2, it was necessary to use optically active sulfinylimine that is difficult in industrial availability, and trimethyl(trifluoromethyl)silane (TMSCF3) was a very expensive reagent.
Thus, there was a strong demand for a process that is capable of industrially producing optically active 1-alkyl-substituted 2,2,2-trifluoroethylamine.